1. Field of the Invention
The present invention relates to a light emitting diode package, and more particularly, to a light emitting diode package capable of emitting light of a mixed color and being driven under AC power.
2. Discussion of the Background
Since development of GaN-based light emitting diodes (LEDs), the GaN-based LEDs have considerably changed LED technologies and are currently used in a variety of applications such as full-color LED display devices, LED traffic lights and white LEDs. High-efficiency white LEDs are expected to become a substitute for fluorescent lamps. Particularly, the efficiency of the white LEDs has reached the level similar to that of typical fluorescent lamps.
In general, an LED emits light by forward current and receives a supply of a direct current (DC) power source. Hence, if the LED is connected directly to an alternating current (AC) power source, the LED is repeatedly turned on and off depending on the direction of current. As a result, the LED does not continuously emit light and may be easily broken by reverse current.
In order to solve such a problem, an LED capable of being directly connected to a high-voltage AC power source is disclosed in International Application Publication No. WO 2004/023568(A1), entitled “LIGHT-EMITTING DEVICE HAVING LIGHT-EMITTING ELEMENTS” by SAKAI et al.
According to International Application Publication No. WO 2004/023568(A1), LEDs (i.e., light emitting cells) are connected in series on a single insulating substrate such as a sapphire substrate to form LED arrays. Two LED arrays are connected to each other in reverse parallel on the sapphire substrate. As a result, a single-chip light emitting device capable of being directly driven by an AC power supply is provided. Since the single-chip light emitting device is fabricated of a GaN-based compound to emit ultraviolet or blue light, the single-chip light emitting device and a phosphor may be combined to provide an LED package for emitting mixed-color light such as white light.
For example, a white LED package can be implemented by combining a single-chip light emitting device for emitting blue light, a phosphor for emitting yellow light by wavelength-converting blue light or phosphors for emitting green light and red light. However, white light produced from the combination of the blue light emitting device and the yellow phosphor may have poor color reproduction characteristics, and use of the green and red phosphors may cause luminous efficiency to be lowered due to the excessive use of the phosphors.